Process to produce polymers

ABSTRACT

A process to produce ethylene polymers is provided. Particularly, a process to produce ethylene polymers having a broad molecular weight distribution is provided. More particularly, a process to produce ethylene polymers that have low formation of smoke and odor during blow molding is provided.

FIELD OF THE INVENTION

[0001] This invention is related to the field of processes that producepolymers, where said polymers comprise polymerized ethylene. The phrase“ethylene polymers” as used in this application includes homopolymers ofethylene, and copolymers of ethylene with another monomer. Particularly,this invention is related to the field of processes that produceethylene polymers having a broad molecular weight distribution. Moreparticularly, this invention is related to the field of processes thatproduce ethylene polymers that have low formation of smoke and odorduring blow molding.

BACKGROUND OF THE INVENTION

[0002] There are many production processes that produce ethylenepolymers. Ethylene polymers are utilized in many products, such as, forexample, films, coatings, fibers, bottles and pipe. Producers of suchethylene polymers are continuously conducting research to find improvedethylene polymers.

[0003] Ethylene polymers with a broad molecular weight distributiongenerally have excellent processing characteristics such as, forexample, high shear ratio, high shear at onset of melt fracture, lowweight and die swell, and excellent physical properties such as highenvironmental stress crack resistance. However, often times, theseethylene polymers can produce smoke and odors when blow molded intomanufactures.

[0004] This invention provides ethylene polymers having a broadmolecular weight distribution and also low formation of smoke and odorsduring blow molding. Due to these improved properties, these ethylenepolymers are ideal for blow molding bottles and other manufactures.

SUMMARY OF THE INVENTION

[0005] It is an object of this invention to provide a process topolymerize ethylene, or to copolymerize ethylene with at least one othermonomer, to produce ethylene polymers.

[0006] It is another object of this invention to provide said ethylenepolymers.

[0007] It is another object of this invention to provide ethylenepolymers having high environmental stress crack resistance and lowformation of smoke and odor during blow molding.

[0008] It is yet another object of this invention to provide a processto use said ethylene polymers to produce a manufacture.

[0009] It is still yet another object of this invention to provide amanufacture comprising said ethylene polymers.

[0010] In accordance with this invention, a process is provided, saidprocess comprising polymerizing ethylene, or copolymerizing ethylenewith at least one other monomer, wherein said polymerizing is conducted:

[0011] in a loop reactor with isobutane as a diluent;

[0012] at a temperature in a range of about 200° F. to about 220° F.;

[0013] with a catalyst system comprising chromium and a support;

[0014] in the presence of at least one trialkylboron;

[0015] wherein the chromium is present in a range of about 1% by

[0016] weight to about 4% by weight based on the weight of the support;

[0017] wherein said support comprises silica and titania;

[0018] wherein said support has a surface area of about 400 m²/gram toabout 800 m²/gram and a pore volume of about 1.8 ml/gram to about 4ml/gram;

[0019] wherein the titania is present in a range of about 0.5% by weightto about 3% by weight titanium based on the weight of the support;

[0020] wherein said catalyst system is activated at a temperature fromabout 1000° F. to about 1300° F.;

[0021] wherein said trialkylboron is represented by the formula, BR₃,

[0022] where R is an alkyl group of up to 12 carbon atoms.

[0023] In another embodiment of this invention, said ethylene polymersare provided.

[0024] In yet another embodiment of this invention, a process for usingsaid ethylene polymers to produce a manufacture is provided.

[0025] In still another embodiment of this invention, a manufacture isprovided comprising said ethylene polymers.

[0026] These and other objects of this invention will become moreevident from the following description and claims.

DETAIL DESCRIPTION OF THE INVENTION

[0027] A process comprising polymerizing ethylene, or copolymerizingethylene with at least one other monomer is provided. Said “at least oneother monomer” can be olefins having from 4 to about 16 carbon atoms permolecule. Suitable monomers, that can be polymerized with ethylene toproduce copolymers with excellent properties, can be selected from thegroup consisting of 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene,1-octene.

[0028] The polymerizing is conducted in a loop reactor process at atemperature in a range of about 200° F. to about 220° F. with isobutaneas a diluent. The loop reactor process is well known in the art and isdisclosed, for instance, in Norwood, U.S. Pat. No. 3,248,179, thedisclosure of which is hereby incorporated by reference.

[0029] The polymerizing is conducted using a catalyst system comprisingchromium and a support. The chromium can be any suitable chromiumcompound that facilitates the polymerization of olefins. Suitableexamples of chromium compounds include, but are not limited to, chromiumnitrate, chromium acetate, chromium trioxide, and mixtures thereof. Theamount of chromium present is from about 1% by weight to about 4% byweight. Preferably, the amount of chromium present is from about 1.5% byweight to about 3.5% by weight, most preferably, from 2% by weight to 3%by weight, where such weight percents are based on the weight of thesupport.

[0030] The chromium can be combined with the support in any manner knownin the art. Examples of combining the chromium with the support can befound in U.S. Pat. Nos. 3,976,632; 4,248,735; 4,297,460; and 4,397,766;the entire disclosures of which are hereby incorporated by reference.

[0031] The term “support” is not meant to be construed as an inertcomponent of the catalyst system. The support used in the catalystsystem of this invention comprises (or alternatively, “consistsessentially of” or “consists of”) silica and titania. These supports areknown in the art and are disclosed in U.S. Pat. Nos. 2,825,721;3,225,023; 3,226,205; 3,622,521; 3,625,864; 3,780,011; 3,887,494;3,900,457; 3,947,433; 4,053,436; 4,081,407; 4,151,122; 4,177,162;4,294,724; 4,296,001; 4,392,990; 4,402,864; 4,405,501; 4,434,243;4,454,557; 4,735,931; 4,981,831; and 5,037,911, the entire disclosuresof which are hereby incorporated by reference. However, it should alsobe noted that these supports are available commercially from suchsources as the W.R. Grace Corporation.

[0032] Generally, the amount of titania present is from about 0.5% byweight to about 3% by weight titanium. Preferably, the amount of titaniapresent is from about 0.8% by weight to about 2.6% by weight titanium,most preferably from 0.8% by weight to 1.5% by weight titanium, wheresuch weight percents are based on the weight of the support.

[0033] The support has a surface area from about 400 m²/gram to about800 m²/gram. Preferably, the support has a surface area from about 450m²/gram to about 700 m²/gram, and most preferably, from 500 m²/gram to600 m²/gram. Furthermore, the support has a pore volume of from about1.8 ml/gram to about 4 ml/gram. Preferably, the support has a porevolume of from about 2 to about 3.5 ml/gram, and most preferably, from2.3 ml/gram to 3 ml/gram.

[0034] The catalyst system used in this invention is activated inaccordance with any manner known in the art that will contact an oxygencontaining ambient with the catalyst system. Suitable examples of thistype of procedure can be found in U.S. Pat. Nos. 3,887,494; 3,900,457;4,053,436; 4,081,407; 4,296,001; 4,392,990; 4,405,501; and 4,981,831,the entire disclosures of which are hereby incorporated by reference.Generally, activation is conducted at a temperature in a range of about1000° F. to about 1300° F. Preferably, activation is conducted at atemperature in a range of about 1050° F. to about 1250° F., and mostpreferably, from 1 100° F. to about 1200° F. Currently, the preferredoxidizing ambient is air. This activation is carried out for a timeperiod of about 1 minute to about 50 hours. This allows for at least aportion of any chromium in a lower valance state to be converted to ahexavalent state.

[0035] The polymerizing is also conducted in the presence of at leastone trialkylboron with a formula, BR₃, where R is an alkyl group of upto 12 carbon atoms. Preferably, said trialkylboron is triethylboron(TEB). The amount of the cocatalyst used in a polymerization, stated inparts per million by weight based on the weight of the diluent in thereactor, is from about 1 part per million to about 6 parts per million.Preferably, it is from about 1.5 parts per million to about 4 parts permillion, and most preferably, it is from 2 parts per million to 3 partsper million.

[0036] Hydrogen can be present in the loop reactor to control molecularweight. Currently, about 0 to about 3 mole percent hydrogen can be used.

[0037] Generally, said ethylene polymers produced by this process havethe following properties: a high load melt index (HLMI) of about 10 toabout 60 grams per ten minutes; a density of about 0.950 to about 0.960grams per cubic centimeter; a shear ratio (high load melt index(HLMI)/melt index (MI)) of about 100 to about 300, a polydispersity(weight average molecular weight (Mw)/number average molecular weight(Mn)) of about 15 to about 30; a Environmental Stress Crack Resistance(ESCR) (Condition A) of greater than 300 hours; xylene solubles of lessthan 1.0%; and a low molecular weight polymer content of less than 2%.Low molecular weight polymer is ethylene polymer with a molecular weightof less than 1000. Test methods to determine these properties aredescribed subsequently in the Examples.

[0038] It is preferred when said ethylene polymers have a HLMI of about15 to about 40 grams per ten minutes, and most preferably, 15 to 30grams per ten minutes.

[0039] It is also preferred when said ethylene polymers have a densityof about 0.952 to about 0.958 grams per cubic centimeter, and mostpreferably, 0.953 to 0.957 grams per cubic centimeter.

[0040] It is also preferred when said ethylene polymers have a shearratio (HLMI/MI) of about 120 to about 200, most preferably, from 130 to180.

[0041] It is also preferred when said ethylene polymers have apolydispersity (Mw/Mn) of about 18 to about 25, and most preferably, of19 to 25.

[0042] It is also preferred when said ethylene polymers have aEnvironmental Stress Crack Resistance (Condition A) of greater thanabout 400 hours, and most preferably, greater than 500 hours.

[0043] It is also preferred when said ethylene polymers have a lowformation of smoke and odor when blow molded into manufactures asindicated by having less than 0.85% xylene solubles and less than 1.6%low molecular weight polymer. Most preferably, said ethylene polymershave less than 0.6% xylene solubles and less than 1% low molecularweight polymer.

[0044] Said ethylene polymers can be used to produce manufactures. Saidethylene polymers can be formed into a manufacture by any means known inthe art. For example, said ethylene polymers can be formed into amanufacture by blow molding, injection molding, and extrusion molding.Further information on processing said ethylene polymers into amanufacture can be found in MODERN PLASTICS ENCYCLOPEDIA, 1992, pages222-298. One important application for said ethylene polymers is theproduction of bottles and other manufactures by blow molding.

EXAMPLES

[0045] These examples are provided to further illustrate the invention.The scope of the invention should not be limited to these examples.

[0046] Test Methods

[0047] A Quantachrome Autosorb-6 Nitrogen Pore Size DistributionInstrument was used to determined the surface area and pore volume ofthe supports. This instrument was acquired from the QuantachromeCorporation, Syosset, N.Y.

[0048] Polymer density was determined in grams per cubic centimeter(g/cc) on a compression molded sample, cooled at about 150° C. per hour,and conditioned for about 40 hours at room temperature in accordancewith ASTM D1505 and ASTM D1928, procedure C.

[0049] Melt index (MI, g/10 minutes) was determined in accordance withASTM D1238 at 190° C. with a 2,160 gram weight.

[0050] High load melt index (ILMI, g/10 minutes) was determined inaccordance with ASTM D1238 at 190° C. with a 21,600 gram weight.

[0051] Environmental Stress Crack Resistance (ESCR, hrs) was determinedaccording to ASTM D1693, Conditions A and B.

[0052] The Heterogeneity Index (HI) was determined using size exclusionchromatography (SEC) analyses that were performed at 140° C. on a Water,model 150 GPC with a refractive index detector. A solution concentrationof 0.25 weight percent in 1,2,4-trichlorobenzene was found to givereasonable elution times. To determine smoke potential of the ethylenepolymer, the amount of ethylene polymer in the <1000 molecular weightrange was calculated.

[0053] Ethylene polymers obtained by this invention are useful for blowmolding applications. In these examples, blow molding evaluations wereconducted by blowing a one gallon (105.1 gm) bottle on a Uniloy 2016single head blow molding machine using a 2.5 inch diameter die, 20degree diverging die, 32% accumulator position, 8.5 second blow time,0.10 second blow delay, 0.75 second pre-blow delay and a 45° F. moldtemperature. A reciprocating screw speed of 45 revolutions per minute(rpm) was used, providing parison extrusion at shear rates greater than10,000/sec through the die.

[0054] Percent weight swell measures the amount a molten polymer expandsimmediately as it exits the die. It is a measure of the “memory” of thepolymer chains as they seek to relax and thus reform the polymer shape.Weight swell is an important parameter as it determines how tight a diegap must be adjusted to provide a constant bottle weight. If a polymerhas high weight swell, the die gap required will be tighter to make aproper part weight.

[0055] In so doing, it will require higher stress to push the polymerthrough the die than a lower weight swell polymer. Weight swell isdefined as the ratio of the die gap to the final bottle wall thickness.

[0056] Another measurement of swell is die swell or diameter swell. Thisis the ratio of a parison diameter to a die diameter. These numbers arereferenced to a standard commercial blow molding polymer, Marlex®5502polyethylene, obtained from Phillips Petroleum Company.

[0057] Bottle stress crack resistance was tested using ten 105 gram onegallon bottles made as described above on a Uniloy 2016 machine. Thebottles were filled with a 10% Orvus-K detergent solution, capped, andplaced in a 140 ° F. hot room. Bottle failures were noted each day, anda 50% mean failure time was calculated for each set.

[0058] Onset of melt fracture of each ethylene polymer was evaluated onthe same Uniloy machine by opening the die gap and extruding theethylene polymer. Shear rate was increased steadily by increasing thescrew rpm. Onset was the rpm at which the parison showed visible signsof melt fracture, such as a shark skin appearance or a distortedsurface.

[0059] Two methods to measure a polymer's ease of processibility wereutilized in these examples. The first, listed as “Output” in the tablespresented subsequently in this disclosure, was calculated from the cycletime of the machine and the weight of the bottle and flashing. Thus,this measure describes the rate of bottle output in pounds of polymerper hour at which the polymer in question was blow molded into bottlesduring normal operation. Therefore, it is a measure of the commercialrate of bottle production. The second measure of polymer processibilityis listed as “1-Minute Output” in the tables presented subsequently inthis disclosure. It describes the speed at which one part of the blowmolding operation was accomplished. For this test, the extruder on theblow molding machine was set at 45 rpm, and it was allowed to extrudepolymer for one full minute at the same die gap used to make the desiredbottles. After 1 minute, the test was stopped, and the polymer wasweight to determine the 1-minute output value. Thus, the 1-minute outputvalue gives an indication of the rate of extrusion of the polymer duringthe blow molding operation.

[0060] Xylene solubles (%) was determined in accordance with ASTMD-5492-94.

[0061] Subjective ratings were also made by the operator running theblow molding machine, in which he judged the degree of smoke and odorproduction by the ethylene polymer during processing, the degree of meltfracture, and the processibility of the ethylene polymer. On this scale,the best ethylene polymers were given a 1 and the worst a 5. Ratings inthe 1 to 3 range were considered acceptable.

Invention Examples 1-5 (Table One)

[0062] Ethylene polymers were prepared by contacting a catalyst systemwith monomers in a continuous, particle form process which employed aliquid full 15.2 cm diameter pipe loop reactor having a volume of 23gallons (87 liters), isobutane as the diluent, and occasionally somehydrogen to regulate the molecular weight of the ethylene polymerproduced. The loop reactor was operated to have a residence time of 1.25hours. The reactor temperature was varied over a range of 95 ° C. to107° C., depending on the particular experiment, and the pressure wasfour Mpa (580 psi). At steady state conditions, the isobutane feed ratewas about 46 liters per hour, the ethylene feed rate was about 30lbs/hr, and the 1-hexene feed rate was varied to control the density ofthe ethylene polymer. Ethylene polymer was removed from the loop reactorat the rate of 25 lbs per hour and recovered in a flash chamber. AVulcan dryer was used to dry the ethylene polymer under nitrogen atabout 60° C. to 80° C.

[0063] Ethylene that had been dried over alumina was used as themonomer. Isobutane that had been degassed by fractionation and driedover alumina was use as the diluent. Triethylboron (TEB) ortriethylaluminum (TEA) was also sometimes used as a cocatalyst asindicated in the tables below.

[0064] In example 1 and 4-6, a commercially available catalyst system,designated 963 Magnapore, was purchased from the W.R. Grace Corporation.It had a chromium content of about 1.0 weight percent based on theweight of the support and about 2.5 weight percent titanium based on theweight of the support. It had a surface area of about 500 to 550 squaremeters per gram and a pore volume of about 2.4 to 2.6 ml/g.

[0065] In examples 2 and 3, another catalyst system was obtained fromW.R. Grace, designated Magnapore-1, which was essentially identical to963 Magnapore except that it contained 1.0 weight percent titanium basedon the weight of the support.

[0066] In some cases, as indicated in the tables below, extra chromiumwas added to the catalyst system. This was accomplished by impregnatingthe catalyst system to incipient wetness or somewhat less, with amethanol solution of chromium (III) nitrate containing 0.05 grams ofchromium per 100 milliliters.

[0067] In Inventive Examples 1-6, the ethylene polymer produced hadbroad molecular weight distributions as shown by having a shear ratio of145 to 250, a polydispersity of 19.8 to 24.7, and a ESCR (Condition A)of 321 to greater than 1000 hours. In addition, the ethylene polymershave a low percentage of low molecular weight polymer (0.44%-1.97% byweight), and xylene solubles (0.20%-0.96%), thereby having low smoke andodor when blow molded into manufactures.

COMPARATIVE EXAMPLES 1-15 (TABLE TWO)

[0068] Ethylene polymers were prepared in the same loop reactor andunder the same process parameters as described above except the amountof titanium and cocatalyst, the surface area, and the pore volume werevaried outside the limits of this invention.

[0069] Various catalysts and cocatalysts were used in these runs asindicated in the table and descriptions below.

[0070] In comparative examples 1-5 and 12, a commercially availablecatalyst system, designated 964 Magnapore, was purchased from the W.R.Grace Corporation. It had a chromium content of about 0.8 weight percentbased on the weight of the support and about 5 weight percent titaniumbased on the weight of the support. It had a surface area of about 550to 600 square meters per gram and a pore volume of about 2.1 to 2.3ml/g.

[0071] In comparative example 6, a catalyst system was obtained from theW.R. Grace Corporation, designated HPVSA indicating its relatively highpore volume and surface area compared to standard 969MS grades. It had asurface area of 577 square meters per gram and a pore volume of 2.21ml/g.

[0072] In comparative examples 7-9, a commercially available catalystsystem, designated 963 Magnapore, was purchased from the W.R. GraceCorporation. It had a chromium content of about 1.0 weight percent basedon the weight of the support and about 2.5 weight percent titanium basedon the weight of the support. It had a surface area of about 500-550square meters per gram and a pore volume of about 2.4-2.6 ml/g.

[0073] In comparative example 9, a commercially available catalystsystem was purchased from the W.R. Grace Corporation. This catalystsystem was sold under the name of 965 Sylopore. It had surface area ofabout 400 square meters per gram and a pore volume of about 1.0 ml/g.

[0074] In comparative example 10, titanium was added to a 969MS catalystsystem obtained from W.R. Grace Corporation by first drying the 969MScatalyst in dry nitrogen in a fluidized bed at 400-500° F., thenlowering the temperature to 250° F.-400° F. during which time titaniumisopropoxide liquid was added over a period of about one hour. Thetitanium isopropoxide evaporated while transported by the nitrogen in a⅛″ stainless steel coil which introduced the vapor into the bottom ofthe bed. After all the titanium had been added, the nitrogen gas streamwas replaced by dry air, and the temperature was increased to thedesired activation temperature in the usual fashion. The final catalystcomposition was analyzed after activation.

[0075] In comparative example 11, a catalyst system was obtained fromW.R. Grace Corporation designated HPV silica. It had a surface area ofabout 300 square meters per gram, and a pore volume of about 2.5 ml/g.

[0076] In comparative example 13, a commercially available catalystsystem was purchased from the W.R. Grace Corporation called 969MS. Thiscatalyst had a surface area of about 300 square meters per gram, and apore volume of about 1.6 ml/g.

[0077] As can be seen in Table Two, the objects of this invention, suchas, low smoke and odor potential, high ESCR, low swell, and high shearat melt fracture are not achieved when the catalyst system and operatingparameters of this invention are not met. Thus, in comparative runs 1-5and 12, where the titanium content of the catalyst system was too high,the molecular weight distribution became too broad as indicated by theshear ratio (HLMI/MI) and polydispersity (Mw/Mn) giving excessively highsmoke and odor formation as indicated by high low molecular weightcontent and xylene solubles.

[0078] In contrasting runs 6, 11, and 13, where the titania was too low,the molecular weight distribution was not broad enough (HLMI/MI andMw/Mn) which led to poor ESCR, swell or output.

[0079] Likewise, surface area, pore volume, activation temperature, andcocatalyst are also varied in the table with the result that desiredethylene polymer properties were not obtained if the catalyst system andoperating parameters were varied outside of the prescribed bounds ofthis invention. In Run 8, cocatalyst was not used, and the ethylenepolymer produced had a low ESCR. In Runs 9 and 10, a catalyst systemhaving lower surface area and pore volume than specified in theinvention produced ethylene polymer having a lower shear ratio and ESCR(Condition A). Chromium content affects swell, as does surface area andpore volume. Cocatalyst affects ESCR, as does activation temperature.Titanium content affects the production of smoke when the ethylenepolymer is blow molded into manufactures. TABLE ONE Invention ExampleNo. 1 2 3 4 5 6 % Titanium (Ti) 2.5 1.0 1.0 2.5 2.5 2.5 % Chromium (Cr)2.0 2.0 2.0 2.0 2.0 2.0 Surface Area 540 560 560 540 540 540 (SA) (m²/g)Pore Volume 2.6 2.7 2.7 2.6 2.6 2.6 (PV (ml/g) Activation Temp. 11001100 1200 1200 1100 1000 (° F.) Cocatalyst TEB/ TEB TEB TEB TEB TEB TEACocatalyst 2.3/2.3 1.94 2 2.05 2 2 (ppm by weight) Productivity (g/g)1504 6250 1558 7143 5882 7692 HLMI (g/10 min.) 21.8 15.2 19.7 12.5 17.219.2 Shear Ratio 145 217 164 250 191 175 (HLMI/MI) Density (g/ml) 0.95470.9557 0.956 0.9537 0.9559 0.9545 Polydispersity 22.7 19.8 22.8 23.421.4 24.7 (Mw/Mn) ESCR-A (hrs) 1000 441 321 >1000 >1000 >1000 ESCR-B(hrs) 100 120 76 180 144 241 Bottle ESCR (hrs) NA NA NA NA >700 >700 DieSwell (%) 46 42.9 45 40.3 44.9 46.4 Weight Swell (%) 409 338 404 386 414436 Shear Rate at 1504 1183 1558 2090 2234 2227 onset of Melt Fracture(sec⁻¹) Output (lbs/hr) 81.6 86.1 86.1 79.8 71 54.8 % Low Molecular 0.850.91 0.44 1.58 1.43 1.97 Weight (<1000) Smoke Rating 2 2 2 3 3 3 (1-5)Melt Fracture 2 2 2 3 2 2 Rating (1-5) Odor Rating 3 3 3 3 3 3 (1-5) 1minute Output 915 711 1125 1257 1343 1339 (grams) Xylene Solubles 0.200.56 0.52 0.92 0.80 0.96 (%)

[0080] TABLE TWO Comparative Example #: 1 2 3 4 5 6 7 Deviative VariableHigh Ti High Ti High Ti High Ti High Ti Low Ti TEA % Titanium (Ti) 2.52.5 5 5 5 0 2.5 % Chromium (Cr) 2 1 1 2 3 2 2 Surface Area (SA) (m²/g)540 400 555 550 555 577 540 Pore Volume (PV) (mug) 2.6 1 2.11 2.26 2.112.21 2.6 Activation Temp. (° F.) 1100 1100 1000 1100 1000 1000 1100Cocatalyst (ppm by weight) None TEB TEB TEB TEB TEB TEA Conc. (ppm) 02.1 2 2 4 2 2 Productivity (g/g) 16667 2600 3571 5556 5882 8333 4167HLMI (g/10 min.) 20.1 22.9 17.2 14.9 17.4 19.3 17 Shear Ratio (HLMI/MI)87 81 191 248 291 138 113 Density (g/ml) 0.9586 0.955 0.9567 0.95450.0564 0.9541 0.9533 Polydispersity (Mw/Mn) 12.6 16.8 38.8 41.9 43.914.4 24 ESCR-A (hrs) 209 170 >1000 >1000 >1000 395 400 ESCR-B (hrs) 4592 429 170 261 73 85 Bottle ESCR (hrs) >700 >700 >700 >700 >700 >70 DieSwell (%) 38 42.6 43.9 40.1 45.4 45.1 Weight Swell (%) 410 395 434 457375 325 Shear Rate at onset of Melt Fracture 2194 2200 2196 2169 22411031 (sec⁻¹) Output (lbs/hr) 59.3 70.2 56.1 58.8 58 85.2 82 % LowMolecular Weight (<1000) 2.42 2.34 2.44 3.73 2.92 0.62 1.22 Smoke Rating(1-5) 4 4 3 3 4 2 2 Melt Fracture Rating (1-5) 4 4 2 2 4 2 2 Odor Rating(1-5) 5 5 4 3 5 2 2 1 minute Output (grams) NA NA NA 1321 NA 1348 620Xylene Solubles (%) 1.20 0.80 1.07 1.12 1.10 NA 0.6 Comparative Example#: 11 12 13 Deviative 8 9 10 Low Ti and Hi Ti and All Variable no TEBLow PV Low SA SA TEA Variables % Titanium (Ti) 2.5 2.5 3 0 5 0 %Chromium (Cr) 2 1 1 2 2 1 Surface Area (SA) (m²/g) 540 400 300 300 555285 Pore Volume (PV) (ml/g) 2.6 1 1.6 2.5 2.11 1.5 Activation Temp. (°F.) 1100 1100 1250 1200 1100 1450 Cocatalyst (ppm by weight) None TEBTEB TEB TEA None Conc. (ppm) 0 2.1 6.2 2 2 0 Productivity (g/g) 166672600 9091 10000 2000 HLMI (g/10 min.) 20.1 22.9 37.3 15.7 16.7 26.2Shear Ratio (HLMI/MI) 87 81 128.6 157 139 79 Density (g/ml) 0.9586 0.9550.958 0.9544 0.9545 0.0547 Polydispersity (Mw/Mn) 12.6 16.8 22 14.2 30.26.3 ESCR-A (hrs) 209 170 200 248 304 <115 ESCR-B (hrs) 45 92 50 61 102<50 Bottle ESCR (hrs) NA 245 180 508 >700 114 Die Swell (%) 51 44 41.344.1 39.3 Weight Swell (%) 353 35 334 330 375 Shear Rate at onset ofMelt Fracture 1014 601 2437 1624 2460 (sec⁻¹) Output (lbs/hr) 85.9 84.583.7 81.4 % Low Molecular Weight (<1000) 0 0.51 2.83 0 Smoke Rating(1-5) 2 2 3 2 Melt Fracture Rating (1-5) 2 2 3 2 Processing (1-5) 3 2 32 Odor Rating (1-5) 3 2 3 1480 1 minute Output (grams) 428 1465 976Xylene Solubles (%) 0.28 NA 0.75

That which is claimed is:
 1. A process comprising polymerizing ethylene,or copolymerizing ethylene with at least one other monomer, wherein saidpolymerizing is conducted: in a loop reactor with isobutane as adiluent; at a temperature in a range of about 200° F. to about 220° F.;with a catalyst system comprising chromium and a support; in thepresence of a trialkylboron; wherein the chromium is present in a rangeof about 1% by weight to about 4% by weight based on the weight of thesupport; wherein said support comprises silica and titania; wherein saidsupport has a surface area of about 400 m²/gram to about 800 m²/gram anda pore volume of about 1.8 ml/gram to about 4 ml/gram; wherein thetitania is present in a range of about 1% by weight to about 4% byweight based on the weight of the support; wherein said catalyst systemis activated at a temperature from about 1000° F. to about 1300° F.;wherein said trialkylboron is represented by the formula, BR₃, where Ris an alkyl group of up to 12 carbon atoms.
 2. A process according toclaim 1 wherein the amount of chromium present is from about 1.5% byweight to about 3.5% by weight, where such weight percents are based onthe weight of the support.
 3. A process according to claim 2 wherein theamount of titania present is from about 0.8% by weight to about 2.6% byweight titanium, where such weight percents are based on the weight ofthe support.
 4. A process according to claim 3 wherein the support has asurface area from about 450 m²/gram to about 700 m²/gram.
 5. A processaccording to claim 4 wherein the support has a pore volume from about 2to about 3.5 ml/gram.
 6. A process according to claim 5 wherein saidactivation is conducted at a temperature in a range of about 1050° F. toabout 1250° F.
 7. A process according to claim 6 wherein the amount ofthe cocatalyst used in a polymerization, stated in parts per million byweight based on the weight of the diluent in the reactor, is from about1.5 parts per million to about 4 parts per million.
 8. A processaccording to claim 7 wherein the amount of chromium present is from 2%by weight to 3% by weight, where such weight percents are based on theweight of the support.
 9. A process according to claim 8 wherein theamount of titania present is from about 0.8% by weight to 1.5% by weighttitanium, where such weight percents are based on the weight of thesupport.
 10. A process according to claim 9 wherein the support has asurface area from 500 m²/gram to 600 m²/gram.
 11. A process according toclaim 10 wherein the support has a support has a pore volume of from 2.3ml/gram to 3 ml/gram.
 12. A process according to claim 11 wherein saidactivation is conducted at a temperature in a range of 1100° F. to 1200°F.
 13. A process according to claim 12 wherein the amount of thecocatalyst used in a polymerization, stated in parts per million byweight based on the weight of the diluent in the reactor, is from 2parts per million to 3 parts per million.
 14. A process according toclaim 13, wherein said trialkylboron is triethylboron.
 15. A processaccording to claim 14 wherein said other monomer is selected from thegroup consisting of 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene,1-octene.
 16. A process according to claim 15 wherein said polymerizingis conducted in the presence of hydrogen.
 17. Ethylene polymers producedby the process in claim
 1. 18. Ethylene polymers having the followingproperties: a HLMI of about 15 to about 40 grams per ten minutes; adensity of about 0.952 to about 0.958 grams per cubic centimeter, ashear ratio (HLMI/MI) of about 120 to about 200, a polydispersity(Mw/Mn) of about 18 to about 25, a Environmental Stress Crack Resistance(Condition A) of greater than 400 hours, less than 0.85% xylenesolubles, and less than 1.6% low molecular weight polymer.
 19. A processaccording to claim 18 wherein said ethylene polymers have the followingproperties: a HLMI of 15 to 30 grams per ten minutes; a density of 0.953to 0.957 grams per cubic centimeter, a shear ratio (ILMI/MI) of 130 to180, a polydispersity (Mw/Mn) of 19 to 25, a Environmental Stress CrackResistance (Condition A) of greater than 500 hours, less than 0.6%xylene solubles and less than 1% low molecular weight polymer.
 20. Aprocess of using said ethylene polymer in claim 1 to produce amanufacture.
 21. A manufacture produced by the process in claim
 20. 22.A manufacture according to claim 21 wherein said manufacture is a bottlehaving a low smoke rating.